This invention relates to methods of depositing films, such as metal oxide films, especially barium-strontium-titanate (BST) films on substrates, particularly semiconductor device structures.
Capacitors are the basic energy storage devices in random access memory devices, such as dynamic random access memory (DRAM) devices, static random access memory (SRAM) devices, and now ferroelectric memory (FE RAM) devices. They consist of two conductors, such as parallel metal or polysilicon plates, which act as the electrodes (i.e., the storage node electrode and the cell plate capacitor electrode), insulated from each other by a dielectric material (a ferroelectric dielectric material for FE RAMs).
High quality thin oxide films of metals, such as barium-strontium-titanates and strontium-bismuth-tantalates, for example, deposited on semiconductor wafers have recently gained interest for use in memories. These materials have very high dielectric constants and excellent resistance to fatigue. They also have suitable properties for a variety of other uses, such as electrooptic materials, pyroelectric materials, and antireflective coatings.
Suitable metal oxides are typically delivered to a substrate in the vapor phase; however, many oxides are difficult to deliver using vapor deposition technology. Many precursors are sensitive to thermal decomposition. Also, many precursors have vapor pressures that are too low for effective vapor deposition. Thus, there is a continuing need for methods and materials for the deposition of oxide films using vapor deposition processes on semiconductor structures, particularly random access memory devices.
The present invention is directed to complexes and methods for forming metal-containing films on substrates, such as semiconductor substrates or substrate assemblies during the manufacture of semiconductor structures, particularly memory devices. The method involves forming a film using a complex having one or more tris(pyrazolyl)borate ligands (referred to herein as pyrazolyl complexes). Typically and preferably, the film is a dielectric metal-containing material. The metal-containing film can be an oxide, sulfide, selenide, telluride, nitride, or combination thereof, for example. Preferably, the film is a metal-containing oxide film. The film can be used as a dielectric layer in an integrated circuit structure, particularly in a memory device such as a ferroelectric memory device.
The methods involve vaporizing a precursor composition comprising one or more, and preferably, two or more,pyrazolyl complexes and directing it toward a substrate, such as a semiconductor substrate or substrate assembly, using a chemical vapor deposition technique to form a metal-containing film on a surface of the substrate, wherein the pyrazolyl complex includes one or more anionic tris(pyrazolyl)borate ligands of the formula: 
wherein the R1, R2, R3, and R4 groups are each individually H, an organic group, or a halide (preferably, the R4 group is H or an organic group). Preferably, the pyrazolyl complex includes one or more ligands of Formula I attached to a metal selected from the group of the Group IIA (i.e., Group 2) metals, the Group IVB (i.e., Group 4) metals, the Group VA (i.e., Group 15), and the Group VB (i.e., Group 5) metals. More preferably, such complexes are of the following formulas: ML2 (Formula II), M(O)L2 (Formula III), M(OR5)xL4xe2x88x92x (Formula IV), and M(OR5)yL5xe2x88x92y (Formula V), wherein M is as defined above, L is the ligand of Formula I as defined above, each R5 group is independently an organic group, x is 2 to 4 (preferably, 2 or 3), and y is 2 to 5 (preferably, 3 or 4). For certain of the preferred embodiments, the precursor composition includes at least one pyrazolyl complex that includes a metal selected from the group of Zr, Hf, V, Nb, and Ta.
The pyrazolyl complexes are neutral complexes and may be liquids or solids at room temperature, but they are typically solids. If they are solids, they are preferably sufficiently soluble in an organic solvent or have melting points below their decomposition temperatures such that they can be used in flash vaporization, bubbling, microdroplet formation techniques, etc. However, they may also be sufficiently volatile that they can be vaporized or sublimed from the solid state using known chemical vapor deposition techniques. Thus, the precursor compositions of the present invention can be in solid or liquid form. As used herein, xe2x80x9cliquidxe2x80x9d refers to a solution or a neat liquid (a liquid at room temperature or a solid at room temperature that melts at an elevated temperature). As used herein, a xe2x80x9csolutionxe2x80x9d does not require complete solubility of the solid; rather, the solution may have some undissolved material, preferably, however, there is a sufficient amount of the material that can be carried by the organic solvent into the vapor phase for chemical vapor deposition processing.
Methods of the present invention are particularly well suited for forming films on a surface of a semiconductor substrate or substrate assembly, such as a silicon wafer, with or without layers or structures formed thereon, used in forming integrated circuits. For example, the methods can involve manufacturing a memory device by providing a substrate having a first electrode thereon, vaporizing a precursor composition and directing it toward the substrate to form a dielectric layer comprising an oxide film on the first electrode of the substrate, and forming a second electrode on the dielectric layer.
It is to be understood that methods of the present invention are not limited to deposition on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. Also, methods of the present invention can be used in silicon-on-insulator technology. Furthermore, substrates other than semiconductor substrates or substrate assemblies can be used in methods of the present invention. These include, for example, fibers, wires, etc. If the substrate is a semiconductor substrate or substrate assembly, the films can be formed directly on the lowest semiconductor surface of the substrate, or they can be formed on any of a variety of the layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term xe2x80x9csemiconductor substratexe2x80x9d refers to the base semiconductor layer, e.g., the lowest layer of silicon material in a wafer or a silicon layer deposited on another material such as silicon on sapphire. The term xe2x80x9csemiconductor substrate assemblyxe2x80x9d refers to the semiconductor substrate having one or more layers or structures formed thereon.
A particularly preferred embodiment of the present invention is a method of forming a film using a liquid precursor composition (typically, a solid pyrazolyl complex dissolved in an organic solvent). The liquid precursor composition includes one or more pyrazolyl complexes of Formulas II-V, which may be liquids or solids dissolved in an organic solvent, for example. The liquid precursor composition may also include other complexes of the metals of Groups IIA, IVB, VA, and VB that do not include any ligands of Formula I. The method involves vaporizing the precursor composition to form vaporized precursor composition; and directing the vaporized precursor composition toward the substrate to form a film on the substrate. Herein, vaporized precursor composition includes vaporized molecules of pyrazolyl complexes described herein either alone or optionally with vaporized molecules of other compounds in the precursor composition, including solvent molecules, if used.
The present invention further provides a chemical vapor deposition precursor composition comprising one or more, and preferably, two or more, pyrazolyl complexes described herein. Also provided are complexes of Formulas III-V.